Mobile robots and their control system

ABSTRACT

System of guidance and positioning relative to a fixed station ( 1 ) for an autonomous mobile robot ( 7 ) utilizing at least a directional infra-red beam ( 2 ′) emitted by the fixed station, the mobile robot being provided with a directional system of detection ( 10   a   , 10   b ) of infra-red emission connected to a microcomputer incorporated in the robot, the robot moving on a work surface in an essentially random manner, the microcomputer ( 44 ) including an algorithm able to control the return to fixed station ( 1 ) by displacement of the robot ( 7 ) towards the direction of emission of said infra-red beam ( 2 ′), characterized in that the infra-red beam ( 2 ′) is a narrow directional beam and in that the system of detection ( 10   a   , 10   b ) is located on a frame at the center of rotation of the robot ( 7 ), oriented in the direction of movement of the robot, precise positioning in the fixed station ( 1 ) being carried out by rotation of the machine around a vertical axis according to an algorithm based on the detection of the narrow beam ( 2 ′).

This application is the national phase of international applicationPCT/BE98/00185 filed Nov. 27, 1998 which designated the U.S.

FIELD OF THE INVENTION

The present invention relates to an autonomous mobile robot, preferablya robot for cleaning, and a system of control of a robot able to guideit towards a fixed station and/or able to adapt its behavior to thelocal degree of dirtiness and/or comprising a rotary brush and able torelease the robot after the blocking of the aforementioned brush.

The invention relates more particularly to a system of guidance of thepath of an autonomous mobile robot, including its positioning withrespect to, and the approach towards, a fixed station of recharge inenergy or discharge of elements collected by the robot. It will be, mostfrequently but not exclusively, a robot for cleaning the ground, whichis provided with rechargeable batteries, for example a robotic vacuumcleaner. However it can also be a robot for spreading a substance or amonitoring robot.

An autonomous mobile robot, for example supplied with batteries,presents a limited autonomy. If one wants to obtain a continuousoperation, the robot must be able to recharge its batteries at regularintervals of time. Other functions can also require the regular accessto a fixed point for example the unloading of a bag of dust (robot-likevacuum cleaner) or resupplying in fuel (thermal engine) or in a productto be spread.

A solution to this problem has already been disclosed (seeEP-A-0744093), wherein the mobile machine, sensitive to the gradient ofan electromagnetic field, repositions itself automatically to thevertical of a coil traversed by a AC current.

In the case of surfaces comprising disturbing elements for theelectromagnetic field (steel reinforcement of concrete for example), theabove system operates with difficulty.

It can then be preferable to associate with the fixed station aninfra-red radiation source (transmitting LED) allowing the mobilemachine to locate the station remotely.

DESCRIPTION OF THE RELATED ART

U.S. Pat. No. 4,679,152 discloses an autonomous mobile robot able toautomatically return to a recharging station when the level of charge ofa battery decrease below a predetermined threshold. The rechargingstation and the mobile robot are provided with a infra-read beamtransmitter and a system of detection connected to a microcomputer, Therobot and the recharging station may thus communicate in abi-directional way There is provided a search program with anopto-acoustic system which may involve a random moving of the robot onthe work surface. Such system is complicated and appears to be poorlyefficient when a very accurate positioning of the robot relative to therecharging station is required for the recharging operation. The purposeof the present invention is to overcome this drawback by providing,according to the simplest embodiment, a system using a narrow beamemitted by the recharging station, detectable by a directional sensorlocated on the chassis at the center of rotation of the robot.

According to a first aspect of the invention, a relatively narrow beam,varying for example between 2 and 10° preferably approximately 5°,emerges from the fixed station. The corresponding transmitter and theassociated station are preferably oriented so that the beam extends overa maximum length of the work surface of the robot. The mobile robot,provided with a system of directional detection of infra-red emission,is moving substantially in a random way on this surface, crosses anddetects the narrow beam in statistically periodic manner.

According to a preferred embodiment, if some duration of work isexceeded, eg 15 to 45 minutes, whatever the state of load of thebattery, the robot will return towards the fixed station for a cycle ofrecharge or refill as soon as it crosses an infra-red beam of a givenintensity. If it is near the station after the above-mentioned durationof work, it will join it and will thus start a reload. This processavoids the operation of seeking the beam when the state of the batterydecreases below a predetermined level. The narrowness of the beam allowsa precise final positioning relative to the fixed station, and thusallows, for example, a recharging operation by induction or more simplyby physical contact of conductors.

BRIEF SUMMARY OF THE INVENTION

As the working time increases, the algorithm of the microprocessorperforms so that the threshold of intensity of the infra-red beam to bedetected by the mobile robot decrease in a linear way or by increment,in order to initiate the return step.

The stage of return can cause the discontinuance of all the functions ofthe robot which are not essential in order to find the station ofrecharge or refill.

According to another embodiment or the invention, the system of guidanceand of positioning is based upon at least two beams of differentdirectionality property emerging from the fixed station, the beam(s)lees directional being used for the approach towards the fixed station,while the more directional beam is used for the ultimate stage ofprecise positioning of the robot relative to this fixed station Thisalternative allows the guidance of the robot in a more complexenvironment (e.g. an apartment with several rooms, with several doors).

The transmitter of the less directional beam is located at a level ofthe fixed station so that its influence decreases at the ultimate stageof approach and of positioning of the robot. It can be manually directedas desired and located at the end of an overhanging arm above the frontpart of the fixed station itself.

In the phase of positioning, the transmitter will thus be advantageouslylocated above the robot, the beam emitted being then out of thedetection plane of the sensors of the robot. The latter, by a movementof rotation around its center, is then able to determine a finalposition of recharge, for example with physical contact, while basingitself on the signal of the transmitter of stronger directionalitylocated in the detection plane of the sensors of the robot. The power ofthe beams can be different, the moat powerful beam being generally butnot necessarily the least directional beam.

The robot includes a directional system of detection of infra-redemission, for example comprising at least two directional sensors forwhich intensities of signals are compared, in a known way, by amicrocomputer to control a rotation towards the source of emission.These sensors are preferentially located on the chassis at the center ofthe robot, oriented in the direction of movement of the robot. Possibly,one or several other sensors may be provided, for example on thelateral. Sides or on the rear side, advantageously having directionaldetection system substantially opposed to that of the central sensors.Advantageously also, the beams to be recognized by the sensors of therobot will be modulated in order to avoid any background noise.

According to this aspect of the invention, there is proposed a system oflocation and positioning relative to a fixed station for an autonomousmobile robot moving in a room characterized in that the fixed stationemits two modulated infra-red beams, primarily in the plane of therooms, one of the beams being appreciably more directional than theother. The least directional transmitter beam allows the location andthe approach of the fixed station by the mobile robot provided withdirectional sensors sensitive to these beams. The signals of the sensorsare treated by one microcomputer controlling the advance of the mobilerobot, the transmitter of weaker directionality being located on thefixed station at a position perpendicular to the mobile robot when thelatter joins its desired position in the fixed station, the moredirectional beam is then able to be detected in a more sensitive way bythe aforementioned sensors, precise positioning being carried out byrotation of the machine about a vertical axis according to an algorithmbased on the detection of the narrow beam.

According to an alternative one proposes a system of location and ofpositioning at a fixed station for a mobile autonomous robot moving in aroom characterized in that the fixed station emits at least threeinfra-red modulated beams, one of the beams being appreciably moredirectional than the others. Transmitters of the least directional beam;and generally moreover stronger intensity, allows the location and theapproach to the fixed station by the mobile robot carrying thedirectional sensors directional sensitive to the known as beams. Signalsfrom the sensors are treated by a microcomputer controlling the advanceof the mobile robot, the transmitters of less directionality beingoriented and being located on the fixed station such that the beamscross each other in the immediate vicinity of the station. The mostdirectional beam, which can be of lesser intensity, is then able to bemore easily detected by the aforementioned sensors, precise positioningbeing carried out by rotation of the machine around a vertical axisaccording to an algorithm based on the detection of the narrow beam.

According to still another embodiment, the modulation of the beamsemitted by the fixed station, including then a microcomputer, cantransmit information to the robot, or to one robot among others ifseveral robots are used with the same central station. This informationcan refer to availability of the station for a recharge operation an/ordischarge, or can constitute an instruction relating to the workingmethod, or to stopping or recall of the robot, sound localization of therobot etc. Possibly one can also envisage a transmission in returntowards the fixed station, with the assistance of an intra-redtransmitter carried by the robot.

The present invention also relates to a technique of guidance for thevacuum-cleaning of ground of dust, applicable to the autonomous robotsused for cleaning.

Document EP-A-0769923 discloses a mobile autonomous machine for thevacuum-cleaning of ground, of low power and of small size allowing it tocover easily a surface encumbered by, for example, pieces of furniture.

The recharge of the batteries of the robot is advantageously coupledwith the discharge of accumulated dust.

The content of the above-mentioned document is incorporated by referencein the present description.

The low power of this auction robot does not always allow however tocarry out a thorough cleaning in only one passage. It can thus benecessary when the machine is over a particularly dirty surface, toenvisage a longer time of passage (for example passing from a velocityof 20 cm/sec to 10 cm/sec) and/or to have additional passages to cleansurface completely.

To this end, according to another aspect of the invention, a particulartechnique of cleaning is provided, such technique being applicable toany autonomous robot used for vacuum-cleaning and/or brushing.

The technique of guidance for the cleaning of ground by a robotic vacuumcleaner is indeed characterized in that the path followed by the robotdepends on the quantity of particles present on the surface to clean,the aforementioned quantity being estimated by an analyzer of particleslocated near the opening of suction, or in one cavity of brushing of therobot, the aforementioned analyzer sending signals to a microcomputercarried by the mobile robot and controlling the displacement of therobot according to the said signals.

In addition, the aforementioned analyzer of particles can have thefunction of determining the degree of filling of the dust tank. If dustaccumulates beyond a certain point the same infra-red beam located afterthe suction opening, that is to say at the level of the tank precedingthe filter, will be stopped, which the microcomputer will interpret as acorresponding signal.

According to the measured quantity of aspired dust, the microcomputercan for example control one deceleration and/or a linear forth and backmovement of the mobile robot.

The microcomputer can also control a movement of systematic cleaning,for example a forth and back movement in fan order.

Advantageously the microcomputer can take into account the size of theparticles and their number, according to the amplitude and the frequencyof the signals emitted by the analyzer of particles. An analysis of thetype of dust collected, thanks to the knowledge of the size of thegrains and of their number, makes it possible to refine the robots'behavior by correcting its path, the number of revolutions of the brushand/or the power of the vacuum cleaner turbine.

The analyzer of dust comprises for example a transmitter and a receiver,preferably in the infra-red.

The microcomputer can advantageously keep in memory a global average ofthe level of dust detected by the sensor of dust on a long distance, theactivation of a particular cleaning algorithm taking account of theaforementioned average.

Moreover, advantageously, the suction robot can include a sensor of dustwherein one or several elements are periodically or constantlyautomatically cleaned by a flow of air oriented towards its surface.

According to another aspect of this invention the autonomous robot is arobot including a rotary brush.

The invention thus proposes a surface cleaning robot comprising aselement of cleaning at least a rotary brush, and comprising amicrocomputer controlling at least, via an algorithm, the velocityand/or the path of the robot characterized in that the microcomputer isassociated with an algorithm which take account, to determine theaforementioned speed and/or the aforementioned path, of at least of therotational velocity of the aforementioned rotary brush. The robot forcleaning is typically a robotic vacuum-cleaner.

Advantageously, the microcomputer of the robotic vacuum-cleaner takesaccount,in order to determine the power of aspiration, of the rotationalspeed of the aforementioned rotary brush. The suction power can interalia be dependent on the number of revolutions of the aforementionedbrush.

The microcomputer is therefore able to take account of the measurementof number of revolutions of the motor to determine the behavior of theaforesaid robot.

The presence of a rotary brush presents however the disadvantage ofseeing the brush blocking itself when it meets, for example, the fringesof a carpet laid out on the surface to clean.

A solution with this problem was described in the patent application PCTWO 97/40734 and consists in reversing the direction of rotation of thebrush so as to release it.

The solution of the present application has the advantage of notrequiring a precise control of the brush, nor the inversion of its wayof rotation. This simplifies the design of the robot. This more simplesolution appeared to be more effective in practice.

The device according to the intention includes a system comprising arotary brush—driven by a motor—activated by microcontroller (ormicrocomputer) controlling the whole of the functions of the autonomousrobot. Reference is made in this respect at the patent application PCTWO 96/01072 incorporated herein by reference.

The number of revolutions of the brush is analyzed by themicrocontroller, preferably constantly.

This measurement can be carried out according to several knowntechniques (measurement of the consumed current by the motor in the caseof a dc motor, measurement of frequency of the impulses in the case of amotor without brushes, optical coder).

The measurement of this number of revolutions allows the microcontrollerto deduce certain information concerning, for example, the nature of thecleaned surface or the occurrence of an incident and to adapt therobot's behavior consequently.

At the time of occurrence of an incident such as the halt of the rotarybrush, caused for example by the rolling up of fringed of a carpetaround the axis of the brush, the microcontroller will disconnect thebrush and will cause the robot to start a series of operations ofdisengagement.

This operation can be, according to the design of the robot, onemechanical disengagement but will be preferably an electricdisconnection of the motor.

As an example some particularly efficient maneuvers are describedhereafter.

The robot moves back of a distance equal to its diameter (brushesdisconnected). By doing this the fringes exert one effort of unfoldingon the axis of the brush which is in free wheel.

The brush is released. The retreat brings the robot outwards of the zoneof the fringe. The robot rotates then while re-engaging the brush. If,at this stage, the brush is still blocked, it stops its rotationalmovement and the robot performs a new retreat to again attempt to permitthe rotation of the brush and so on until the brush is released.

The maximum number of reiterations is fixed by the program and by themaximum free distance for retreat of the robot.

If this maximum distance is reached without the brush being released,the robot will continue the iterations but in forward motion.

If no operation succeeds in releasing the brush, the robot is put in awaiting status associated to a signal, and a manual intervention isnecessary.

Advantageously, the analysis of the number of revolutions of the brushalso makes it possible to know the nature of the ground cleaned.

A high number of revolutions reflects a smooth ground, a slower speedreflects a surface covered with a carpet. The slower the speed, thethicker the carpet. This analysis allows the robot to adapt its velocityin advance and to adapt the suction power according to the nature of theground to be cleaned.

The invention can be applied to cleaning robots other than vacuumcleaners, for example to robots for cleaning unspecified surfaces withliquids or to robots to wax parquet floors.

The invention thus relates also to a cleaning robot comprising a rotarybrush and a microcomputer, a means for detecting the blocking of therotary brush which is associated to the microcomputer, an algorithm ofdisengagement of the robot, a means of disengaging the rotary brushrelative to the associated motor, the algorithm including causing amovement of retreat of the robot followed by a rotation and theresumption of the forward movement of the robot.

The means of disengagement consists advantageously in a disconnection ofthe motor from its electrical supply.

In short, the robot for cleaning a surface according to one aspect ofthe invention comprises at least a rotary brush, the speed and/or thepath and/or possibly the suction power of a turbine, being dependent onthe revolution speed of the aforementioned rotary brush.

For a robotic vacuum-cleaner, in particular a domestic one, therotational movement of the brush takes place preferably in a verticalplane relative to the surface to be cleaned.

The invention relates also to method of operation of a cleaning robot asabove-mentioned, the blocking of the rotary brush being detected by theaforementioned microcomputer which controls then an operation forreleasing the robot. The aforementioned releasing operation comprises atleast a disengagement of the said rotary brush relative to the motoroperating it, coupled to a movement of retreat of the robot followed bya rotation and the resumption of the forward moving of the robot. Theoperation possibly includes several cycles ofdisengaging-retreat-rotation-forward movement.

According to still another aspect of the invention, which can be appliedto any autonomous mobile robot, more advantageously to robots of greatdimension (p.e. 80 to 250 cm), the robot comprises a linear sensor ofcollision surrounding entirely or partly the lower portion of thecareenage in the plane of movement, The sensor is made of a metalliclinear conductor and, in parallel, a linear plastic conductorelement,for example made out of conducting rubber. The unit can beincluded in a sheath or an insulating flexible membrane fixed along theedge of body. For example, the linear elements are fixed by gluing twointernal opposite faces of the sheath. These two elements are separatedby a small distance The ends of the conducting plastic are subjected toa potential difference, for example of 5 volt, that is to say 0 volt atan end and 5 volt at the other end. At the occurrence of a collision ofthe robot with a frontal or lateral obstacle, one of the two elements isable to come elastically into contact with the other element under theeffect of a temporary pressure resulting from the impact of the robotwith the obstacle. It will be understood that the instantaneous voltageon the conducting element is a function of the distance from the pointof impact to one of the end of conducting plastic, which has a higherresistance. Thus a measured voltage of 2.5 volt means that the impacttook place roughly at the middle of the linear sensor. The measuredvoltage at the level of the conducting element thus constitute a signalsent to the microcomputer in order to locate the point of impact at thebasis of careenage.

The improvements according to the invention are to be applied moreparticularly to mobile robots moving, in their mode of normal operation,in a random way without any system of precise positioning.

The various aspects of the invention will be better understood with theadditional description which follows, which refers to the annexeddrawings provided as examples only, and thus without limiting the scopeof the additional description Each described feature, taken separately,may be generalized in accordance with the knowledge of the expert.Identical number references in the drawings relates to identicalequivalent elements.

In the drawings,

FIG. 1 schematically represents a side view of the fixed stationcomprising two infra-red transmitters,

FIG. 2 schematically represents a top view of the fixed station,

FIG. 3 represents schematically a top view of an alternative embodimentof the fixed station

FIG. 4 represents schematically the station and one approaching mobilerobot,

FIG. 5 represents schematically a top view of a circular mobile robot,

FIG. 6 is a diagrammatic sectional view of the front of a suction unitof a robot provided with a brush according to the invention and of asystem of detection of dust,

FIG. 7 is a diagrammatic side view of a robot with a brush according tothe invention

FIG. 8 is a view illustrating the technique of cleaning

FIG. 9 is a side view of a robotic vacuum cleaner with a brush

FIG. 10 is a front view of the robot of FIG. 9

FIG. 11 illustrates an algorithm of disengagement resulting from theblocking of the brush

FIGS. 12a to 12 c illustrate a method of localization of the point ofimpact of the robot with an obstacle.

While referring to FIGS. 1 and 2, the fixed station 1 comprise twoinfra-red beam generators 2,3 The infra-red light is modulated at afrequency of a few kilocycles (p.e. 56 KHz). The station comprises atransmitter IR 2 emitting a narrow beam from approximately 5°, of lowpower, and a transmitter IR 3 emitting a broad beam possiblyomnidirectional, of higher power. Transmitter 3 is located so that themobile machine can freely position itself below it, its center ofrotation being able to face the origin of the beam 3′. The transmittercan thus be placed at the end of an arm 4 overhanging the base, ordocking plate for the robot, of the recharge station.

According to another embodiment illustrated at FIG. 3, the origin of thebeam 3′ can possibly be one virtual origin 3 a obtained by the crossingat the point 3 a of two beams of origin 3 b and 3 c.

The fixed station comprises the various elements necessary for itsfunction: for example, for a vacuum cleaner, a system for recharging thebattery comprising contacts 5 and discharge outlet 6.

The mobile robot 7 illustrated schematically in FIGS. 4 and 5 is arobotic vacuum cleaner comprising one or several rechargeable batteries.The robot is essentially circular and comprises two driving wheels 8,allowing in particular a rotation about its central axis. There will benoted the presence of a circular ring for side reinforcement of the body90.

There is shown, laid out in a circle, the exit openings 16 of theturbine of the vacuum cleaner. Also shown are two driving wheels 8 a, 8b operated by both motors 12 a, 12 b, and small free casters 13 near thesuction inlet (not illustrated).

The machine comprises in its center of rotation at least one directionalinfra-red sensor 10, preferably two (10 a, 10 b), in the latter casepreferably forming between them an angle equal to their detection angle.The one or several sensors are oriented in the direction of the forwardmovement of the mobile machine. Additional sensors 11 a, 11 b directeddifferently, preferably backward, can advantageously complete thedevice. The location of this or of these additional sensors does nothave to be at or near the center of rotation of the machine. Signalscoming from the various sensors arc amplified, filtered and directed tothe microprocessor controlling the movement of the machine, by theintermediary of one A/D converter. Lobes of sensitivity of detection(directionality) are illustrated in dotted lines.

The signals can possibly be multiplexed that is to say analyzedsequentially by the microcomputer carried in the robot, each signalbeing connected in its turn with the chain of amplification and ofconversion by means of an electronic switch.

The infra-red beam of strong power 3′ covers a part of the surface onwhich the machine moves. The beam covering is obtained either directlyif there is no obstacle in the pathway of the beam, or indirectly byreflection or diffraction in the contrary case. This allows the IR lightto penetrate in parts of the space not being in direct eight of thesource. The use of broad and high power beams allows the full coveringof for example rooms communicating by doors. In very complexenvironments, it can be useful, in addition, to lay out reflectors oreven repeaters.

The mobile machine moving in a essentially random manner, there isalways during its displacement a moment when one of its two sensors willdetect the I.R. signal, either coming straight from the source or byreflection.

The microcomputer will then control, in a known way, a rotation of themachine in order to obtain the same signal on the two frontal sensors 10a and 10 b and a minimal signal at the back (this in the case of the useof 3 or more sensors, 11 a, 11 b).

The microcomputer will then make the machine progress towards the originof the signal, i.e. the fixed station 1. This latter aspect of thetechnique of “homing” is known in itself.

If the signal comes from a reflection, at one moment the machine movingtowards the point of reflection will meet the direct beam emitted bytransmitter 2 (see FIGS. 1-4), or a radiation of a degree of reflectionless than the one originally sensed. It will then rotate automaticallytowards the source signal after balancing the signals of its two frontalsensors 10 a, 10 b.

Once arrived near the fixed station, the mobile machine 7 will came to aposition so as to make coincide the sensors located at its center ofrotation (frontal sensors 10 a, 10 b) in the vicinity of the origin ofthe beam 3.

Its approach being able to be made from several directions, its positionwill probably not be adequate to realize an electric connection viaconnectors 5, 5′ with the charger, or any other operations. At thispoint of time the narrow beam 2′ of low power will play its role.Arriving at the level of the generator 3, the signal collected by thesensors 10 a, 10 b decreases considerably and becomes definitely lessstrong than the signal coming from narrow beam 2′. Indeed the sensorsare not omnidirectional and are not conceived, in particular, fordetecting effectively an infra-red signal in the vertical directionrelative to the surface of displacement.

Machine 7 will thus rotate on itself to align the sensors with beam 2′and to start again its progression in such a way to position accuratelyon the fixed station, and to allow thus, for example, a physicalelectric connection via connectors 5, 5′ for recharging the batteries.

Another aspect of this invention is illustrated in FIGS. 6 to 8.

FIG. 6 is a diagrammatic front sectional view of the suction unit of therobot supported by an element of chassis 35, which is a variant of FIGS.4 and 5. The robot is provided with a brush roller 24 made up of brushes25 turning around an axis 26.

There is shown in FIG. 7 a turbine 20 for the suction, driving wheels21, a filter 21, the circular area 29 covered by the transmitter 27,said area being centered on sensor 28, and infra-red sensors 10 a, 10 b.Arrows in FIG. 7 indicate the path of the air in the robotic vacuumcleaner.

The particular device for the detection of dust according to aembodiment the invention is provided in the mobile robot and comprisestwo parts:

an analyzer of dust on the one hand made up of one infra-redtransmitting element 27 and of a infra-red detecting element 28. Thesetwo elements are laid out on one and the other side of the suction inlet29 and are located along their mutual axis. When dust is sucked orprojected by the rotary brush roller 24, there is created a diffractionin the beam 27′, while passing between the transmitting element and thedetecting element, generating in that way a variation of signal at theoutput of the detecting element 28.

The amplitude of the variation of the signal is roughly proportional tothe size of the particles and to the number of particles passing throughthe beam each second.

This signal, after amplification by a logarithmic amplifier, is analyzedby the microcomputer controlling the machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The value of the average intensity of the beam at the receiver is alsocommunicated to the microcomputer.

On the other hand, the microcomputer is associated with a programallowing to react in accordance with the data communicated by theabove-mentioned analyzer.

The operation of the machine according to this mode of operation isdescribed hereafter.

When the machine moves on the surface to clean, the signal coming fromthe dust sensor is constantly analyzed by the microcomputer. The latterwill make the machine run, for example, in the following way:

If the dirty surface is small (detection of particles on a distance lessthan 1 cm), the machine decrease its speed so as to increase the time ofcleaning it the relevant zone. This variation of speed can also berelated to the dimension and the frequency of detected grains.

If the dirty surface is more important (detection of particles at adistance for example between 1 and 5 cm), the machine carries out a backand forth movement until there is no more dust to detect. It resumesthen its forward movement.

If finally dirty surface is sufficiently important (for example morethan 5 cm), the machine returns in one systematic mode of cleaning asdescribed in FIG. 8.

In FIG. 8 the distance D is the effective width of suction of machine 7.

The machine, guided by the microcomputer, starts by mating an outwardand return movement to determine the total length of spot 30. Oncereturned to its starting point 31, it performs a rotation to the rightby an angle α which depends on the length of the spot. The machineprogresses up to the edge of spot 30 and returns to its starting point31 in order to carry out a new rotation to the right so on until theright part of the spot is cleaned (absence of detection of particles).It takes again the direction of the axis of the spot while turning leftby one angle equal to the sum of the increments carried out towards theright-hand side and reiterates the same scenario starting from thecenter but towards the left.

DETAILED DESCRIPTION OF THE INVENTION

When an absence of particles is detected on the left, it returns incenter 31 and resume its normal progression.

Other algorithms of systematic cleaning can to be adopted (spiral pathetc.), in a lens preferred manner.

The level of dirtiness being able to strongly differs from a room to theother, it can be interesting to start the process of systematic cleaningas described previously only if the level of instantaneous dirtiness isdefinitely higher than the average level of the room. This is realizedby keeping in memory a global average of level of dust as detected bythe dust sensor on a long distance.

According to another aspect, the arrangement for dust detection can beassembled in such a way that a flow of vacuum-cleaned air or air withoutdust is directed towards the sensor and/or the transmitter 27, 28 toprevent the fast dirt accumulation.

This flow is brought for example by channels 22 provided in the wallopening in an outlet located under the sensor and/or the transmitter.Alternatively, in a manner presently less preferred, the flow of air canbe brought by a duct deviating some of the air exiting the turbine.

Dirt accumulation could however occur and so cause a decrease of theamplitude of the received signal. This dirt accumulation is detected bythe microcomputer thanks to the second signal coming from the sensor(being average intensity of the beam). The microcomputer can either takeaccount of this accumulation of dirt by automatically compensating thereadings, or act on the infra-red transmitter in such a way to keepconstant the average illumination of the receiver.

FIGS. 9 and 10 illustrate the components of a robotic vacuum cleanerwith a brush roller and with detection of dust according to anotherembodiment of the invention.

There is shown a turbine 20 with the associated motor 41 in order tosuck the air and the dust from the inlet suction 29. There is also showna first filter 23 a, and a second, finer filter 23 b, the driving wheels8 a and 8 b, and the geared motors 12 a, 12 b and one pair of casters13, motor 48 for the brush roller 24, the container 42 for dust, frontIR sensors 10 and bumper 91 on body 90. There is also illustrated theintegrated circuits board 43 supporting the microprocessor 44. At FIG.10, there is shown more precisely the suspension springs 50 a, 50 b withtwo arms (with axis 51 a, 51 b) and articulated supports 52, 52 a forthe motors 12 a, 12 b.

FIG. 11 is a diagram illustrating a example of algorithm according tothe invention, being operated in the case of blocking of the brushroller of the robot.

FIGS. 12a to 12 c represents an arrangement for the detection of thepoint of impact of the robot with an obstacle. FIG. 12a is transversesection, FIG. 12b is a longitudinal section and FIG. 12c represents theelement 61, 62 at the perimeter of the robot 7 (sheath 60 is not shown).

The base or lower part of the robot is essentially surrounded, in theplane of movement, by a hollow linear insulating element 60. Thiselement 60 includes internally and longitudinally a flexible linearresistive element 61 made via adhesive 63 with an external part, byrelative to the robot, of the internal side. This element is a resistiveelement made up of a conducting rubber. The ends of this resistiveelement are subjected to a potential difference of 5 V. Opposite to thisresistive element 61 there is provided a metallic conducting element 62possibly attached to 60 also by joining. An impact with an obstacle 65on element 60 will cause a resilient contact between the resistiveelement 61 and the conducting element 62. The measurement of the voltageon the conductor makes it possible to determine the distance D and thusto deduce the location of the impact. It will be understood that thistechnique of detecting a point of impact can be applied largely in thefield of the mobile robots. For certain applications one can alsoenvisage several elements 60 in different planes.

The invention refers to any new element disclosed in the presentspecification, that the expert will understand suitable to be consideredseparately or in combination.

What is claimed is:
 1. System of guidance and positioning relative to afixed station (1) for an autonomous mobile robot (7) utilizing at leasta directional infra-red beam (2′) emitted by the fixed station, themobile robot being provided with a directional system of detection (10a, 10 b) of infra-red emission connected to a microcomputer incorporatedin the said robot, the robot moving on a work surface in an essentiallyrandom manner, the microcomputer (44) including an algorithm able tocontrol the return to fixed station (1) by displacement of the robot (7)towards the direction of emission of said infra-red beam (2′),characterized in that the infra-red beam (2′) is a narrow directionalbeam and in that the system of detection (10 a, 10 b) is located on aframe at the center of rotation of the robot (7), oriented in thedirection of movement of the robot, precise positioning in the fixedstation (1) being carried out by rotation of the machine around avertical axis according to an algorithm based on the detection of thenarrow beam (2′).
 2. System of guidance according to claim 1 in whichthe narrow directional beam (2′) has an angle ranging between 2 and 10°.3. System according to claim 1 characterized in that it utilizes atleast two beams (2′, 3′) of substantially different directionalityemitted from or in the vicinity of the fixed station (1), the one orseveral least directional beams (3′) being used for the approach towardsthe fixed station (1), while the one or several more directional beams(2′) are used for the ultimate step of precise positioning of the robotrelative to the fixed station (1).
 4. System according to claim 1wherein the algorithm of the microcomputer initiates the return towardsthe fixed station of recharge after a minimum working time,independently of the state of charge of a battery, and when the mobilerobot detects an infra-red radiation of an intensity higher than acertain threshold, the aforementioned threshold decreasing with theincrease in the duration of the working time and/or when the state ofcharge of the battery is below a predetermined level.
 5. Systemaccording to claim 1 wherein the algorithm of the microcomputerinitiates the return towards the fixed station of recharge when thestate of load of the battery is under a predetermined level.
 6. Systemaccording to claim 1 characterized in that during the step of return ofthe robot towards the fixed station, and according to the state ofcharge of the battery and/or the intensity of the detected infra-redradiation, the brush roller and/or the suction turbine are inactivated.7. System for direction finding and positioning according to claim 1characterized in that the fixed station emits two modulated infra-redbeams (2′, 3′), essentially in a plane of a room wherein the said robot(7) moves, one of the beams being appreciably more directional than theother, a transmitter of the least directional beam allowing the findingof direction and approach of the fixed station by the mobile robotcarrying directional sensors (10 a, 10 b, 11 a, 11 b) sensitive to saidbeams, the signals of the sensors being treated by one microcomputer(44) controlling the advance of the mobile robot, the transmitter (3) ofthe last directional beam being located on the fixed station (1) suchthat it is directly above the mobile robot when the latter joins itsdesired position in the fixed station, the more directional beam (2)being then able to be more intensively detected by the said sensors,precise positioning being carried out by rotation of the machine arounda vertical axis in accordance with an algorithm based on the detectionof the narrow beam.
 8. System for direction finding and positioningaccording to claim 1 characterized in that the fixed station emits atleast three modulated infra-red beams (2′, 3′), one (2) of the beamsbeing appreciably more directional than the other beams, thetransmitters (3 b, 3 c) of the last directional beams allowing thefinding of the direction and the approach of the fixed station by themobile robot carrying directional sensors sensitive to said beams, thesignals of the sensors being treated by one microcomputer (44)controlling the advance of the mobile robot, the transmitter of highintensity being oriented and located in the fixed station at a locationsuch that the beams cross (2′, 3′) each other in the immediate vicinityof the station, the more directional beam being then able to be moreintensively detected by the aforementioned sensors, the precisepositioning being carried out by rotation of the machine around avertical axis in accordance with an algorithm based on the detection ofthe narrow beam.
 9. System according to claim 1 wherein the transmitterof the more directional infra-red beam (2) is less powerful than thetransmitter (3) of the less directional infra-red beam.
 10. Autonomousmobile robot incorporating a microcomputer (44) able to apply the systemof claim
 1. 11. Robot according to claim 10 comprising at least a rotarybrush roller (24) and a microcomputer (44) controlling at least, via analgorithm, the speed and/or the path of robot characterized in that themicrocomputer is associated with an algorithm which takes into account,in order to determine the aforementioned speed and/or the aforementionedpath, the measurement of the rotation speed of the aforementioned rotarybrush roller.
 12. Robot for cleaning according to claim 11 characterizedin that it is a robotic vacuum-cleaner.
 13. Robot according to claim 12characterized in that the microcomputer (44) takes at least in account,for determining the suction power, the measurement of number ofrevolutions of the aforementioned brush roller (24).
 14. Robot accordingto claim 13 incorporating a guiding technique for the cleaning of theground characterized in that the path followed by the robot (7) dependson the quantity of particles present on the surface to clean, the saidquantity being estimated by a particle analyzer (27, 28) located nearthe suction inlet of the robotic vacuum cleaner, the aforementionedanalyzer sending the signals to the microcomputer (44) carried by themobile robot and controlling the displacement of the robot according tothe said signals.
 15. Robot according to claim 14 wherein themicrocomputer can control a deceleration and/or a linear back and forthmovement and/or a back and forth movement in a fan shape of the mobilerobot.
 16. Robot according to claim 13 wherein the microcomputer keepsin memory a global average of dust level as detected by the sensor (27,28) of dust on a long distance, the activation of one particularalgorithm for cleaning taking account of the aforementioned average. 17.Robot according to claim 1 characterized in that it comprises a linearsensor of collision surrounding entirely or partly the base of thecareenage, the sensor including a linear metal (62) conductor and, inparallel, a linear element (61) made of conducting plastic, for exampleconducting rubber, whose ends are subjected to a potential difference,the linear element in plastic being able to come elastically intocontact with the conducting linear element under the effect of atemporary pressure resulting from the impact of the robot with anobstacle (65), the measurement of the current measured at the level ofthe conducting element being a signal fed to the microcomputer to locatethe point of impact at the basis of the careenage.